Add instructions about OpenH264 in the readme

README.md

@@ -11,10 +11,24 @@ distributions, in MacPorts for Mac OS X (http://www.macports.org/) and/or from
 http://cmake.org/
 - to install git (available in the package systems of Linux distributions, in 
 MacPorts for Mac OS X (http://www.macports.org/) and/or from http://cmake.org/
+- you also need 7-zip to generate SDK packages (http://www.7-zip.org/)
 
 ## AVAILABLE BUILD TARGETS
 
 The following targets are supported:
+- Linphone for desktop platforms
 - Linphone for BlackBerry10 - see README.bb10
 - Liblinphone Python extension module - see README.python
-- Flexisip and dependencies - see README.flexisip.md
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+- Flexisip and dependencies - see README.flexisip.md
+
+## OpenH264 support
+OpenH264 support is enabled in all generated installers and SDK archive.
+However, the OpenH264 runtime library must be downloaded directly from
+Cisco's websit to be complient with H264 patents. In the case of linphone GTK+,
+it is automatically done by the Windows and MacOS installers. In the case of
+SDKs of linphone and mediastreamer, you must manualy download the OpenH264 archive
+and extract it in the "bin" directory of the SDK distribution and rename the DLL
+file into "openh264.dll".
+
+The pattent free OpenH264 runtime library archive is available here:
+http://ciscobinary.openh264.org/openh264-1.4.0-win32msvc.dll.bz2
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